This invention generally relates to electrical transformers, and more specifically to three-phase padmounted transformer with a specially designed rib and gasket for preventing the insertion of extraneous objects in cabinet area of such transformers.
In recent years many new residential and commercial developments in both the U.S. and foreign countries have recognized the beneficial attributes of underground electrical service and have emphasized the use of such service. Systems of this type eliminate the need for pole lines and above-ground wiring which inherently detract from the overall appearance of both residential as well as commercial developments. Adoption of such underground electrical systems has necessitated the development of above-ground transformers which are not raised by utility poles but are positioned on ground surface platforms. Because these transformers are often positioned on the property of resident owners, the most significant problem facing the use of platform-mounted or padmounted transformers is that they may fascinate children and lure them into tampering with such transformers. Further, such transformers may be subjected to vandals who may attempt to pry open the transformer by inserting an extraneous object into an interface between components of the transformer. Consequently, there is an ever-present need to provide tamper-resistant padmounted transformers which can be safely and confidently placed in residential areas.
The necessity of tamper-resistant padmounted transformers has been recognized in the art as is shown in U.S. Pat. No. 4,267,399 issued to Robert J. Lux, Jr. Therein, a hollow sleeve is positioned about the cables which enter and exit the cabinet portion of the transformer. The sleeve extends above the top surface of the cement pad such that wires or other long slender implements which are pushed between the lower edge of the transformer housing and the top surface of the pad are prevented from contacting the cables. However, the sleeve cannot prevent extraneous objects from being inserted into the seam interface between the cabinet and tank of the transformer.
In U.S. Pat. No. 4,556,758, issued to Gary A. Warden, and assigned to Westinghouse Electric Corporation, a tamper-resistant cabinet-to-tank interface is disclosed. Therein, a hinged joint is required at the cabinet-to-tank interface with the interface being formed by two equal, oppositely facing acute angles formed in the cover, an a single obtuse angle. When the cabinet is pivoted about the hinged joint, a leg of the obtuse angle enters the vertex of an acute angle thereby creating an obstructed path whereby any elongated objects, such as a wire, cannot be readily extended into the cabinet-to-tank interface. However, with the above-mentioned interface, hinges are required to hold the two components together and form the only contact between the cabinet and cover. Care must be taken during the manufacture of such an interface to ensure proper alignment between the obtuse and cooperating acute angles.
With three-phase transformer cabinetry as is shown in FIG. 1, the cabinet portion of the transformer extends above the tank portion and includes a lockable front door for allowing authorized personnel access to the interior of the cabinet. A back baffle of the cabinet is bolted to an upper side portion of the transformer, as shown in FIG. 3, with a cork gasket positioned therebetween to prevent foreign objects from being inserted into the cabinet at the cabinet-to-tank interface. However, with the cork gasket, additional adjustment is sometimes required at assembly due to misalignments of tank and cabinet.
In view of the foregoing, it is clear that there is a need for both an economical and a more reliable construction for preventing unauthorized intrusion at the cabinet-to-tank interface of a padmounted three-phase transformer resulting in a tamper-resistant unit which may be safely and confidently used in both commercial and residential areas.